// Copyright (c) 2013 Pieroxy <pieroxy@pieroxy.net>// This work is free. You can redistribute it and/or modify it// under the terms of the WTFPL, Version 2// For more information see LICENSE.txt or http://www.wtfpl.net///// For more information, the home page:// http://pieroxy.net/blog/pages/color-finder/index.html//// Detection of the most prominent color in an image// version 1.1.1
function ColorFinder(colorFactorCallback) {  this.callback = colorFactorCallback;  this.getMostProminentColor = function(imgEl) {    var rgb = null;    if (!this.callback) this.callback = function() { return 1; };    var data = this.getImageData(imgEl);    rgb = this.getMostProminentRGBImpl(data, 6, rgb, this.callback);    rgb = this.getMostProminentRGBImpl(data, 4, rgb, this.callback);    rgb = this.getMostProminentRGBImpl(data, 2, rgb, this.callback);    rgb = this.getMostProminentRGBImpl(data, 0, rgb, this.callback);    return rgb;  };
  this.getImageData = function(imgEl, degrade, rgbMatch, colorFactorCallback) {        var rgb,        canvas = document.createElement('canvas'),        context = canvas.getContext && canvas.getContext('2d'),        data, width, height, key,        i = -4,        db={},        length,r,g,b,        count = 0;        if (!context) {      return defaultRGB;    }        height = canvas.height = imgEl.naturalHeight || imgEl.offsetHeight || imgEl.height;    width = canvas.width = imgEl.naturalWidth || imgEl.offsetWidth || imgEl.width;        context.drawImage(imgEl, 0, 0);        try {      data = context.getImageData(0, 0, width, height);    } catch(e) {      /* security error, img on diff domain */      return null;    }
    length = data.data.length;        var factor = Math.max(1,Math.round(length/5000));    var result = {};        while ( (i += 4*factor) < length ) {      if (data.data[i+3]>32) {        key = (data.data[i]>>degrade) + "," + (data.data[i+1]>>degrade) + "," + (data.data[i+2]>>degrade);        if (!result.hasOwnProperty(key)) {          rgb = {r:data.data[i], g:data.data[i+1], b:data.data[i+2],count:1};          rgb.weight = this.callback(rgb.r, rgb.g, rgb.b);          if (rgb.weight<=0) rgb.weight = 1e-10;          result[key]=rgb;        } else {          rgb=result[key];          rgb.count++;        }      }    }
    return result;
  };    this.getMostProminentRGBImpl = function(pixels, degrade, rgbMatch, colorFactorCallback) {        var rgb = {r:0,g:0,b:0,count:0,d:degrade},        db={},        pixel,pixelKey,pixelGroupKey,        length,r,g,b,        count = 0;            for (pixelKey in pixels) {      pixel = pixels[pixelKey];      totalWeight = pixel.weight * pixel.count;      ++count;      if (this.doesRgbMatch(rgbMatch, pixel.r, pixel.g, pixel.b)) {        pixelGroupKey = (pixel.r>>degrade) + "," + (pixel.g>>degrade) + "," + (pixel.b>>degrade);        if (db.hasOwnProperty(pixelGroupKey))          db[pixelGroupKey]+=totalWeight;        else          db[pixelGroupKey]=totalWeight;      }    }        for (i in db) {      data = i.split(",");      r = data[0];      g = data[1];      b = data[2];      count = db[i];            if (count>rgb.count) {        rgb.count = count;        data = i.split(",");        rgb.r = r;        rgb.g = g;        rgb.b = b;      }    }        return rgb;      };
  this.doesRgbMatch = function(rgb,r,g,b) {    if (rgb==null) return true;    r = r >> rgb.d;    g = g >> rgb.d;    b = b >> rgb.d;    return rgb.r == r && rgb.g == g && rgb.b == b;  }
}